Effects of Strigolactones on Plant Roots

Abstract

Strigolactones are the most recently identified class of plant hormones, having only been classified as phytohormones in 2008. Considerable research has since been conducted on the biosynthesis of these hormones and on their actions in plants, both on the shoots and the roots. Large parts of the biosynthetic pathway have been determined, although several crucial steps which would explain how the different strigolactones arise from a common precursor are still missing. Strigolactones affect the growth and development of all types of roots. Strigolactone action is sensitive to environmental conditions, as the hormones may have virtually opposite effects in the different roots under different carbon and nutrient regimes. Generally, strigolactones enhance root growth when nutrients, particularly phosphate, are limiting but reduce root development when nutrients are abundant. This is also in line with the important role that strigolactones play in promoting the symbiotic relationship between plant roots and arbuscular mycorrhizal fungi, suggesting that strigolactones modify the plant root structure in order to balance carbon use and economy with the ability to obtain sufficient nutrients. In this review, we deal with strigolactone biosynthesis and perception and the role of strigolactones in rooting as well as how interaction of strigolactones with plant nutritional status and other phytohormones determines root architecture.